Ctek Multi XS 3600 rapid flashing amber LED

[itm]

I've been using Ctek Multi XS 3600 for 15 years to keep my S2000 topped up when it's in the garage (which is most of the time). Today I noticed that the middle LED on the top (with the battery half full icon) is flashing rapidly amber. The LED to the right of it (with the battery full icon) is lit solid green as normal, as is the middle LED on the bottom (wet charge mode). I've checked the cable connections to the battery and they seem solid.
Any idea why the middle LED on the top might be flashing rapidly? The battery is less than 1 year old.

[itm]

Aha...it could be....I've rubbed the terminals down and re-connected and I now have a solid charging light. I'll see if it now charges...
Thanks!